| 1. |
- Backs, Alex, et al.
(författare)
-
Development and first results of a magnetic sample environment for polarized neutron imaging of thin metal sheets
- 2023
-
Ingår i: EPJ Web of Conferences. - 2100-014X. ; 286
-
Tidskriftsartikel (refereegranskat)abstract
- Polarized neutron imaging brings the great advantage of analyzing bulk magnetic properties with good spatial resolution. The technique is based on the interaction of the neutron spin with magnetic samples or free magnetic fields and observing the changes to a spin-polarized neutron beam. The high sensitivity to even small magnetic fields is a benefit in obtaining magnetization information but simultaneously a challenge in instrumentation, since magnetic environments for the polarized neutron beam and for the sample, as well as the fringe field from the magnetic sample itself all affect the measurement and can give rise to unwanted effects. We have used finite element simulations and ray tracing simulations, to design and analyze a magnetic sample environment devised for the measurement of ferromagnetic metal sheets. Here we show an analysis of performance of the experimental setup based on the simulation results and compare them to first experimental results on a grain oriented silicon steel sample.
|
|
| 2. |
- Benetti, Ana R, et al.
(författare)
-
How mobile are protons in the structure of dental glass ionomer cements?
- 2015
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- The development of dental materials with improved properties and increased longevity can save costs and minimize discomfort for patients. Due to their good biocompatibility, glass ionomer cements are an interesting restorative option. However, these cements have limited mechanical strength to survive in the challenging oral environment. Therefore, a better understanding of the structure and hydration process of these cements can bring the necessary understanding to further developments. Neutrons and X-rays have been used to investigate the highly complex pore structure, as well as to assess the hydrogen mobility within these cements. Our findings suggest that the lower mechanical strength in glass ionomer cements results not only from the presence of pores, but also from the increased hydrogen mobility within the material. The relationship between microstructure, hydrogen mobility and strength brings insights into the material's durability, also demonstrating the need and opening the possibility for further research in these dental cements.
|
|
| 3. |
- Betz, B, et al.
(författare)
-
Quantification of the sensitivity range in neutron dark-field imaging.
- 2015
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 86:12
-
Tidskriftsartikel (refereegranskat)abstract
- In neutron grating interferometry, the dark-field image visualizes the scattering properties of samples in the small-angle and ultra-small-angle scattering range. These angles correspond to correlation lengths from several hundred nanometers up to several tens of micrometers. In this article, we present an experimental study that demonstrates the potential of quantitative neutron dark-field imaging. The dark-field signal for scattering from different particle sizes and concentrations of mono-dispersive polystyrene particles in aqueous solution is compared to theoretical predictions and the good agreement between measurements and calculations underlines the quantitative nature of the measured values and reliability of the technique with neutrons.
|
|
| 4. |
- Cereser, Alberto, et al.
(författare)
-
Time-of-Flight Three Dimensional Neutron Diffraction in Transmission Mode for Mapping Crystal Grain Structures
- 2017
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- The physical properties of polycrystalline materials depend on their microstructure, which is the nano- to centimeter scale arrangement of phases and defects in their interior. Such microstructure depends on the shape, crystallographic phase and orientation, and interfacing of the grains constituting the material. This article presents a new non-destructive 3D technique to study centimeter-sized bulk samples with a spatial resolution of hundred micrometers: time-of-flight three-dimensional neutron diffraction (ToF 3DND). Compared to existing analogous X-ray diffraction techniques, ToF 3DND enables studies of samples that can be both larger in size and made of heavier elements. Moreover, ToF 3DND facilitates the use of complicated sample environments. The basic ToF 3DND setup, utilizing an imaging detector with high spatial and temporal resolution, can easily be implemented at a time-of-flight neutron beamline. The technique was developed and tested with data collected at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Complex (J-PARC) for an iron sample. We successfully reconstructed the shape of 108 grains and developed an indexing procedure. The reconstruction algorithms have been validated by reconstructing two stacked Co-Ni-Ga single crystals, and by comparison with a grain map obtained by post-mortem electron backscatter diffraction (EBSD).
|
|
| 5. |
- Fedrigo, Anna, et al.
(författare)
-
VESPA : The vibrational spectrometer for the European Spallation Source
- 2016
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 87:6
-
Tidskriftsartikel (refereegranskat)abstract
- VESPA, Vibrational Excitation Spectrometer with Pyrolytic-graphite Analysers, aims to probe molecular excitations via inelastic neutron scattering. It is a thermal high resolution inverted geometry time-of-flight instrument designed to maximise the use of the long pulse of the European Spallation Source. The wavelength frame multiplication technique was applied to provide simultaneously a broad dynamic range (about 0-500 meV) while a system of optical blind choppers allows to trade flux for energy resolution. Thanks to its high flux, VESPA will allow the investigation of dynamical and in situ experiments in physical chemistry. Here we describe the design parameters and the corresponding McStas simulations.
|
|
| 6. |
- Garvey, C. J., et al.
(författare)
-
Small angle neutron scattering on an absolute intensity scale and the internal surface of diatom frustules from three species of differing morphologies
- 2013
-
Ingår i: European Biophysics Journal. - : Springer Science and Business Media LLC. - 0175-7571 .- 1432-1017. ; 42:5, s. 395-404
-
Tidskriftsartikel (refereegranskat)abstract
- The internal nanostructure of the diatoms Cyclotella meneghiniana, Seminavis robusta and Achnanthes subsessilis was investigated using small angle neutron scattering (SANS) to examine thin biosilica samples, consisting of isotropic (powder) from their isolated cell walls. The interpretation of SANS data was assisted by several other measurements. The N-2 adsorption, interpreted within the Branuer-Emmet-Teller isotherm, yielded the specific surface area of the material. Fourier transform infrared (FTIR) and Raman spectroscopy indicates that the isolated material is amorphous silica with small amounts of organic cell wall materials acting as a filling material between the silica particles. A two-phase (air and amorphous silica) model was used to interpret small angle neutron scattering data. After correction for instrumental resolution, the measurements on two SANS instruments covered an extended range of scattering vectors 0.0011 nm(-1) < q < 5.6 nm(-1), giving an almost continuous SANS curve over a range of scattering vectors, q, on an absolute scale of intensity for each sample. Each of the samples gave a characteristic scattering curve where log (intensity) versus log (q) has a -4 dependence, with other features superimposed. In the high-q regime, departure from this behaviour was observed at a length-scales equivalent to the proposed unitary silica particle. The limiting Porod scattering law was used to determine the specific area per unit of volume of each sample illuminated by the neutron beam. The Porod behaviour, and divergence from this behaviour, is discussed in terms of various structural features and the proposed mechanisms for the bio-assembly of unitary silica particles in frustules.
|
|
| 7. |
- Harti, Ralph P., et al.
(författare)
-
Visibility simulation of realistic grating interferometers including grating geometries and energy spectra
- 2017
-
Ingår i: Optics Express. - 1094-4087. ; 25:2, s. 1019-1029
-
Tidskriftsartikel (refereegranskat)abstract
- The performance of X-ray and neutron grating interferometers is characterised by their visibility, which is a measure for the maximum achievable contrast. In this study we show how the real grating geometry in a grating interferometer with three gratings impacts the interference and self projection that leads to visibility in the first place. We quantify the individual contributions of wavelength distributions and grating shapes in terms of visibility reduction by determining the absolute as well as relative effect of each contribution. The understanding of the impact of changed geometry and wavelength distributions on the interference of neutrons/X-rays allows us to present the first fully quantitative model of a grating interferometer setup. We demonstrate the capability of the simulation framework by building a model of the neutron grating interferometer at the ICON beamline and directly comparing simulated and measured visibility values. The general nature of the model makes it possible to extend it to any given grating interferometer for both X-rays and neutrons.
|
|
| 8. |
- Hilger, A., et al.
(författare)
-
Neutron guide optimisation for a time-of-flight neutron imaging instrument at the European Spallation Source
- 2015
-
Ingår i: Optics Express. - 1094-4087. ; 23:1, s. 301-311
-
Tidskriftsartikel (refereegranskat)abstract
- A neutron transport system for the planned imaging instrument ODIN at the future European Spallation Source (ESS) based on neutron optical components was designed and optimized. Different ways of prompt pulse suppression were studied. The spectral performance of the optimal neutron guide configuration is presented. In addition, the influence of the gaps in the guide system needed for the required chopper configuration was investigated. Given that the requirements for an imaging instrument located on a long guide system and hosting a complex chopper system are extremely demanding in terms of spectral and divergence needs, this study can be beneficial for a wide range of instruments in various ways. (C) 2015 Optical Society of America
|
|
| 9. |
- Maimaitiyili, Tuerdi, et al.
(författare)
-
Residual Lattice Strain and Phase Distribution in Ti-6Al-4V Produced by Electron Beam Melting
- 2019
-
Ingår i: Materials. - : MDPI. - 1996-1944. ; 12:4
-
Tidskriftsartikel (refereegranskat)abstract
- Residual stress/strain and microstructure used in additively manufactured material are strongly dependent on process parameter combination. With the aim to better understand and correlate process parameters used in electron beam melting (EBM) of Ti-6Al-4V with resulting phase distributions and residual stress/strains, extensive experimental work has been performed. A large number of polycrystalline Ti-6Al-4V specimens were produced with different optimized EBM process parameter combinations. These specimens were post-sequentially studied by using high-energy X-ray and neutron diffraction. In addition, visible light microscopy, scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) studies were performed and linked to the other findings. Results show that the influence of scan speed and offset focus on resulting residual strain in a fully dense sample was not significant. In contrast to some previous literature, a uniform α- and β-Ti phase distribution was found in all investigated specimens. Furthermore, no strong strain variations along the build direction with respect to the deposition were found. The magnitude of strain in α and β phase show some variations both in the build plane and along the build direction, which seemed to correlate with the size of the primary β grains. However, no relation was found between measured residual strains in α and β phase. Large primary β grains and texture appear to have a strong effect on X-ray based stress results with relatively small beam size, therefore it is suggested to use a large beam for representative bulk measurements and also to consider the prior β grain size in experimental planning, as well as for mathematical modelling.
|
|
| 10. |
- Makowska, Małgorzata, et al.
(författare)
-
Flexible sample environment for high resolution neutron imaging at high temperatures in controlled atmosphere.
- 2015
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 86:12
-
Tidskriftsartikel (refereegranskat)abstract
- High material penetration by neutrons allows for experiments using sophisticated sample environments providing complex conditions. Thus, neutron imaging holds potential for performing in situ nondestructive measurements on large samples or even full technological systems, which are not possible with any other technique. This paper presents a new sample environment for in situ high resolution neutron imaging experiments at temperatures from room temperature up to 1100 °C and/or using controllable flow of reactive atmospheres. The design also offers the possibility to directly combine imaging with diffraction measurements. Design, special features, and specification of the furnace are described. In addition, examples of experiments successfully performed at various neutron facilities with the furnace, as well as examples of possible applications are presented. This covers a broad field of research from fundamental to technological investigations of various types of materials and components.
|
|
| 11. |
- Makowska, Malgorzata Grazyna, et al.
(författare)
-
Coupling between creep and redox behavior in nickel - yttria stabilized zirconia observed in-situ by monochromatic neutron imaging
- 2017
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 340, s. 167-175
-
Tidskriftsartikel (refereegranskat)abstract
- Ni-YSZ (nickel - yttria stabilized zirconia) is a material widely used for electrodes and supports in solid oxide electrochemical cells. The mechanical and electrochemical performance of these layers, and thus the whole cell, depends on their microstructure. During the initial operation of a cell, NiO is reduced to Ni. When this process is conducted under external load, like also present in a stack assembly, significant deformations of NiO/Ni-YSZ composite samples are observed. The observed creep is orders of magnitude larger than the one observed after reduction during operation. This phenomenon is referred to as accelerated creep and is expected to have a significant influence on the microstructure development and stress field present in the Ni-YSZ in solid oxide electrochemical cells (SOCs), which is highly important for the durability of the SOC. In this work we present energy selective neutron imaging studies of the accelerated creep phenomenon in Ni/NiO-YSZ composite during reduction and also during oxidation. This approach allowed us to observe the phase transition and the creep behavior simultaneously in-situ under SOC operation-like conditions.
|
|
| 12. |
- Makowska, Malgorzata G., et al.
(författare)
-
Effect of stress on NiO reduction in solid oxide fuel cells: a new application of energy-resolved neutron imaging
- 2015
-
Ingår i: Journal of Applied Crystallography. - 1600-5767. ; 48, s. 401-408
-
Tidskriftsartikel (refereegranskat)abstract
- Recently, two new phenomena linking stress field and reduction rates in anode-supported solid oxide fuel cells (SOFCs) have been demonstrated, so-called accelerated creep during reduction and reduction rate enhancement and nucleation due to stress (Frandsen et al., 2014). These complex phenomena are difficult to study and it is demonstrated here that energy-resolved neutron imaging is a feasible technique for combined mechanics-chemical composition studies of SOFC components, including commercially produced ones. Cermet anode supports, which prior to the measurements were reduced under varying conditions such as different temperatures, various times and different values of applied stress, have been measured. Thus, samples with different contents (and gradients) of Ni and NiO phases were investigated. The first Bragg edge transmission neutron measurements applied for the studies of the reduction progress in these samples were performed at two neutron beamline facilities (ISIS in the UK, Helmholtz Zentrum Berlin in Germany). The obtained results demonstrate the possibility to image and distinguish NiO and Ni phases within SOFC anode supports by energy-resolved neutron imaging and the potential of the neutron imaging method for in situ studies of reduction processes.
|
|
| 13. |
- Makowska, Malgorzata G., et al.
(författare)
-
In situ time-of-flight neutron imaging of NiO-YSZ anode support reduction under influence of stress
- 2016
-
Ingår i: Journal of Applied Crystallography. - 0021-8898. ; 49:5, s. 1674-1681
-
Tidskriftsartikel (refereegranskat)abstract
- This article reports on in situ macroscopic scale imaging of NiO-YSZ (YSZ is yttria-stabilized zirconia) reduction under applied stress - a phase transition taking place in solid oxide electrochemical cells in a reducing atmosphere of a hydrogen/nitrogen mixture and at operation temperatures of up to 1073K. This process is critical for the performance and lifetime of the cells. Energy-resolved neutron imaging was applied to observe the phase transition directly with time and spatial resolution. Two different approaches are presented for using this imaging technique for the investigation of chemical and physical processes requiring controlled atmosphere and elevated temperature. The first type of measurement is based on alternating stages of short-term partial chemical reaction and longer neutron image acquisition, and the second type is a real in situ neutron imaging experiment. Results of applying energy-resolved neutron imaging with both approaches to the NiO-YSZ reduction investigation indicate enhancement of the reduction rate due to applied stress, which is consistent with the results of the authors' previous research.Results of the first in situ energy-resolved neutron imaging of NiO-YSZ (YSZ is yttria-stabilized zirconia) reduction under applied stress are presented. Neutron experiments were performed at the pulsed neutron source ISIS (UK) using a time-of-flight approach.
|
|
| 14. |
- Nekrassov, D., et al.
(författare)
-
Design of a horizontal neutron reflectometer for the European Spallation Source
- 2014
-
Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 755, s. 85-96
-
Tidskriftsartikel (refereegranskat)abstract
- A design study of a horizontal neutron reflectometer adapted to the general baseline of the long pulse European Spallation Source (ESS) is presented. The instrument layout comprises advanced solutions for the neutron guide, high-resolution pulse shaping and beam bending onto a sample surface being thoroughly adjusted to the properties of the ESS. The length of this instrument is roughly 55 m, enabling delta lambda/lambda resolutions from 0.5% to 10%. The incident beam is focused in horizontal plane to boost measurements of sample sizes of 1 X 1 cm(2) and smaller with potential beam deflection in both downward and upward directions. The primary range of neutron wavelengths utilized by the instrument is 2-7.1 angstrom. If the wavelength range needs to be extended, then this is possible by utilizing only every second (third, fourth) pulse by suppressing all other pulses by the chopper system and thus increase the longest usable wavelength to 12.2 (17.3, 22.4) angstrom. Angles of incidence can be set between 0 degrees and 9 degrees with a total accessible q-range from 4 X 10(-3) angstrom(-1) up to 1 angstrom(-1), while the delta theta/theta resolution can be freely set. The instrument operates in both theta/theta (free liquid surfaces) and theta/2 theta (solid-liquid, air-solid interfaces) geometries. The experimental setup will in particular enable direct studies on ultrathin films (d approximate to 10 angstrom) and buried monolayers to multilayered structures of up to 3000 angstrom total thickness. The horizontal reflectometer will further foster investigations of hierarchical systems from nanometer to micrometer length scale (the latter by off-specular scattering), as well as their kinetics and dynamical properties, in particular under load (shear, pressure, external fields). Polarization and polarization analysis as well as the GISANS option are designed as potential modules to be implemented in the generic instrument layout. The instrument is highly flexible and offers a variety of different measurement modes. With respect to its mechanical components the instrument is exclusively based on current technology. Risks of failure for the chosen setup are minimum. (C) 2014 Elsevier B.V. All rights reserved.
|
|
| 15. |
- Sales, Morten, et al.
(författare)
-
Investigating time-of-flight spin-echo modulation for small-angle neutron scattering through experiments and simulation
- 2015
-
Ingår i: Journal of Applied Crystallography. - 1600-5767. ; 48, s. 92-96
-
Tidskriftsartikel (refereegranskat)abstract
- A spin-echo-modulated small-angle neutron scattering (SEMSANS) instrument in a time-of-flight (TOF) mode will be able to excel at pulsed neutron sources such as the European Spallation Source (ESS), currently under construction. This work compares experimental data from a TOF SEMSANS setup, where a spatial beam modulation of a white beam is obtained using triangular field coils, with Monte Carlo ray-tracing simulations. The experiments and simulations in accordance demonstrate that a good contrast can be achieved when using a constant field in the triangular coils. In the reported setup only neutrons with certain wavelengths rotate by a Larmor precession angle that spatially modulates their polarization to coincide with the period of a grating installed at the detector position. This is shown by measuring with a broad wavelength range while scanning the echo condition.
|
|
| 16. |
- Sales, Morten, et al.
(författare)
-
Wavelength-independent constant period spin-echo modulated small angle neutron scattering
- 2016
-
Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 87:6
-
Tidskriftsartikel (refereegranskat)abstract
- Spin-Echo Modulated Small Angle Neutron Scattering (SEMSANS) in Time-of-Flight (ToF) mode has been shown to be a promising technique for measuring (very) small angle neutron scattering (SANS) signals and performing quantitative Dark-Field Imaging (DFI), i.e., SANS with 2D spatial resolution. However, the wavelength dependence of the modulation period in the ToF spin-echo mode has so far limited the useful modulation periods to those resolvable with the limited spatial resolution of the detectors available. Here we present our results of an approach to keep the period of the induced modulation constant for the wavelengths utilised in ToF. This is achieved by ramping the magnetic fields in the coils responsible for creating the spatially modulated beam in synchronisation with the neutron pulse, thus keeping the modulation period constant for all wavelengths. Such a setup enables the decoupling of the spatial detector resolution from the resolution of the modulation period by the use of slits or gratings in analogy to the approach in grating-based neutron DFI.
|
|
| 17. |
- Strobl, Markus
(författare)
-
General solution for quantitative dark-field contrast imaging with grating interferometers.
- 2014
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- Grating interferometer based imaging with X-rays and neutrons has proven to hold huge potential for applications in key research fields conveying biology and medicine as well as engineering and magnetism, respectively. The thereby amenable dark-field imaging modality implied the promise to access structural information beyond reach of direct spatial resolution. However, only here a yet missing approach is reported that finally allows exploiting this outstanding potential for non-destructive materials characterizations. It enables to obtain quantitative structural small angle scattering information combined with up to 3-dimensional spatial image resolution even at lab based x-ray or at neutron sources. The implied two orders of magnitude efficiency gain as compared to currently available techniques in this regime paves the way for unprecedented structural investigations of complex sample systems of interest for material science in a vast range of fields.
|
|
| 18. |
- Strobl, Markus, et al.
(författare)
-
Quantitative Neutron Dark-field Imaging through Spin-Echo Interferometry.
- 2015
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Neutron dark-field imaging constitutes a seminal progress in the field of neutron imaging as it combines real space resolution capability with information provided by one of the most significant neutron scattering techniques, namely small angle scattering. The success of structural characterizations bridging the gap between macroscopic and microscopic features has been enabled by the introduction of grating interferometers so far. The induced interference pattern, a spatial beam modulation, allows for mapping of small-angle scattering signals and hence addressing microstructures beyond direct spatial resolution of the imaging system with high efficiency. However, to date the quantification in the small angle scattering regime is severely limited by the monochromatic approach. To overcome such drawback we here introduce an alternative and more flexible method of interferometric beam modulation utilizing a spin-echo technique. This novel method facilitates straightforward quantitative dark-field neutron imaging, i.e. the required quantitative microstructural characterization combined with real space image resolution. For the first time quantitative microstructural reciprocal space information from small angle neutron scattering becomes available together with macroscopic image information creating the potential to quantify several orders of magnitude in structure sizes simultaneously.
|
|
| 19. |
- Strobl, Markus, et al.
(författare)
-
The wavelength frame multiplication chopper system for the ESS test beamline at the BER II reactor-A concept study of a fundamental ESS instrument principle
- 2013
-
Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 705, s. 74-84
-
Tidskriftsartikel (refereegranskat)abstract
- Contributing to the design update phase of the European Spallation Source ESS-scheduled to start operation in 2019-a test beamline is under construction at the BER II research reactor at Helmholtz Zentrum Berlin (HZB). This beamline offers experimental test capabilities of instrument concepts viable for the ESS. The experiments envisaged at this dedicated beamline comprise testing of components as well as of novel experimental approaches and methods taking advantage of the long pulse characteristic of the ESS source. Therefore the test beamline will be equipped with a sophisticated chopper system that provides the specific time structure of the ESS and enables variable wavelength resolutions via wavelength frame multiplication (WFM), a fundamental instrument concept beneficial for a number of instruments at ESS. We describe the unique chopper system developed for these purposes, which allows constant wavelength resolution for a wide wavelength band. Furthermore we discuss the implications for the conceptual design for related instrumentation at the ESS. (C) 2012 Elsevier B.V. All rights reserved.
|
|
| 20. |
- Strobl, Markus, et al.
(författare)
-
Using a grating analyser for SEMSANS investigations in the very small angle range
- 2012
-
Ingår i: Physica B: Condensed Matter. - : Elsevier BV. - 0921-4526. ; 407:21, s. 4132-4135
-
Tidskriftsartikel (refereegranskat)abstract
- Spin-echo modulation small-angle neutron scattering (SEMSANS) is based on the detection of spatial beam modulation, which is induced by triangular spin echo precession regions and subsequent spin analyses. In order to detect such signal and exploit it for small angle scattering investigations neutron detection with sub-millimeter spatial resolution is required. Here an approach is reported where instead of a position sensitive detector an absorption grating is used to analyze the beam modulation stepwise. The spin-echo length scan in this case is performed by varying the sample-to-detector distance. The real space correlation functions of reference sample structures in the range 10(2) nm, i.e. giving rise to small-angle scattering in the very small-angle range, are recorded and analyzed successfully. (C) 2012 Elsevier B.V. All rights reserved.
|
|
| 21. |
- Strobl, Stefanie, et al.
(författare)
-
Connected cars : Threats, vulnerabilities and their impact
- 2018
-
Konferensbidrag (refereegranskat)abstract
- The growing demand for interoperability between system components within a connected car has led to new security challenges in automotive development. The existing components, based on established technology, are often being combined to form such a connected car. For such established technologies, individual, often sector specific threat and vulnerability catalogs exist. The aim of this paper is to identify blocks of established technologies in a connected car and to consolidate the corresponding threat and vulnerability catalogs relevant for the individual constituent components. These findings are used to estimate the impact on specific system components and subsystems to identify the most crucial components and threats.
|
|
| 22. |
- Tremsin, A. S., et al.
(författare)
-
Imaging of dynamic magnetic fields with spin-polarized neutron beams
- 2015
-
Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 17
-
Tidskriftsartikel (refereegranskat)abstract
- Precession of neutron spin in a magnetic field can be used for mapping of a magnetic field distribution, as demonstrated previously for static magnetic fields at neutron beamline facilities. The fringing in the observed neutron images depends on both the magnetic field strength and the neutron energy. In this paper we demonstrate the feasibility of imaging periodic dynamic magnetic fields using a spin-polarized cold neutron beam. Our position-sensitive neutron counting detector, providing with high precision both the arrival time and position for each detected neutron, enables simultaneous imaging of multiple phases of a periodic dynamic process with microsecond timing resolution. The magnetic fields produced by 5- and 15-loop solenoid coils of 1 cm diameter, are imaged in our experiments with similar to 100 mu m resolution for both dc and 3 kHz ac currents. Our measurements agree well with theoretical predictions of fringe patterns formed by neutron spin precession. We also discuss the wavelength dependence and magnetic field quantification options using a pulsed neutron beamline. The ability to remotely map dynamic magnetic fields combined with the unique capability of neutrons to penetrate various materials (e.g., metals), enables studies of fast periodically changing magnetic processes, such as formation of magnetic domains within metals due to the presence of ac magnetic fields.
|
|
| 23. |
- Zendler, C., et al.
(författare)
-
Bi-spectral beam extraction in combination with a focusing feeder
- 2013
-
Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 704, s. 68-75
-
Tidskriftsartikel (refereegranskat)abstract
- Bi-spectral beam extraction combines neutrons from two different kinds of moderators into one beamline, expanding the spectral range and thereby the utilization of an instrument. This idea can be realized by a mirror that reflects long wavelength neutrons from an off-axis colder moderator into a neutron guide aligned with another moderator emitting neutrons with shorter wavelengths which will be transmitted through the mirror. The mirror used in such systems is typically several meters long, which is a severe disadvantage because it reduces the possible length of a focusing device in design concepts requiring a narrow beam at a short distance from the source, as used in many instruments under development for the planned European Spallation Source (ESS). We propose a shortened extraction system consisting of several mirrors and show that such an extraction system is better suited for combination with a feeder in an eye of the needle design, illustrated here in the context of a possible ESS imaging beamline. (C) 2012 Elsevier B.V. All rights reserved.
|
|
